An electrode sheet, its preparation method and application

Abstract

The present invention relates to an electrode plate and a preparation method and application thereof. The electrode plate includes a substrate, and a first coating and a second coating are sequentially arranged on the surface of the substrate. The slurry of the first coating includes a low boiling point solvent. The preparation method includes: simultaneously coating the first coating and the second coating on the substrate to obtain a coated electrode plate, and drying the coated electrode plate to obtain the electrode plate. The present invention fundamentally destroys the acting force causing the cracking of the electrode plate, and can adjust the addition amount of the low boiling point solvent according to the drying rate, thereby effectively improving the manufacturing efficiency of thick electrodes.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and relates to an electrode sheet, a preparation method thereof and an application thereof. Background Art

[0002] In view of the problem of cracking of the electrode manufacturing sheet at present, the industry mainly adds plasticizers such as NMP and EC to reduce the surface tension of the slurry, thereby improving the problem of cracking during coating and baking of the negative electrode sheet. The boiling points of the added plasticizers are generally higher than that of the solvent itself, and the solvent remaining in the sheet affects the performance of the battery cell. In addition, high-speed coating of thick electrodes requires a very fast solvent evaporation rate, and the greater the thickness of the electrode, the greater the temperature difference from the surface to the inside of the sheet. The evaporation rate of the surface liquid is fast, while the evaporation rate of the liquid inside the sheet is slow. At this time, simply adding a plasticizer cannot improve the process of sheet cracking.

[0003] CN112133910A discloses a positive electrode slurry for an aqueous lithium iron phosphate battery and a preparation method thereof. The positive electrode active material is lithium iron phosphate, and the binder includes a compound with a main chain of polyethylene glycol and a side chain of acrylate and an acrylic acid-acrylonitrile copolymer. Thereby improving the stability of the slurry, improving the flexibility of the sheet, and solving the problem of sheet cracking and powder falling. However, although the flexibility of the sheet is improved, the improvement of the electrochemical performance of the positive electrode active material is limited.

[0004] CN 111490228A discloses a lithium battery electrode, a preparation method thereof and a lithium battery containing the electrode. The lithium ion battery includes a current collector, an electrochemically active layer provided on the current collector, and a modification layer covering the outer surface of the electrochemically active layer. An ion exchange polymer is used as the modification layer to cover the electrochemically active layer. The modification layer has good shape retention for the electrode, thereby suppressing the pulverization of the material caused by volume change to a certain extent and suppressing the cracking of the sheet to a certain extent. However, the modification layer cannot fundamentally solve the cracking of the sheet, and can only suppress the cracking of the sheet to a certain extent.

[0005] Therefore, how to prepare an electrode sheet and a preparation method thereof that essentially solve the problem of sheet cracking is an important research direction in this field. Summary of the Invention

[0006] The purpose of the present invention is to provide an electrode sheet, a preparation method thereof and an application thereof.

[0007] To achieve the purpose of this invention, the following technical solutions are adopted:

[0008] One of the purposes of the present invention is to provide an electrode sheet, the electrode sheet includes a substrate, a first coating and a second coating are sequentially arranged on the surface of the substrate, and the slurry of the first coating includes a low-boiling solvent.

[0009] During the preparation of the electrode sheet in the present invention, when the sheet is immersed in the oven, the second coating slurry is first heated and the solvent starts to vaporize and evaporate. When the sheet is further heated to the temperature at which the low-boiling solvent in the first coating slurry volatilizes, the low-boiling solvent starts to vaporize, which is equivalent to reducing the partial pressure of the first coating slurry and destroying the capillary force formed in the porous electrode during the solvent evaporation process, fundamentally preventing the cracking of the sheet. The present invention fundamentally destroys the force causing the cracking of the sheet, and the addition amount of the low-boiling solvent can be adjusted according to the drying rate, thereby effectively improving the manufacturing efficiency of the thick electrode.

[0010] As a preferred technical solution of the present invention, the electrode sheet includes a positive electrode sheet and a negative electrode sheet.

[0011] Preferably, the areal density of the positive electrode sheet > 300 g / m 2 , where the areal density can be 310 g / m 2 , 350 g / m 2 , 400 g / m 2 , 450 g / m 2 , 500 g / m 2 , 520 g / m 2 , 540 g / m 2 , 560 g / m 2 , 580 g / m 2 , 600 g / m 2 , 620 g / m 2 , 640 g / m 2 , 660 g / m 2 , 680 g / m 2 , 700 g / m 2 , 750 g / m 2 , 800 g / m 2 or 850 g / m 2 etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable, preferably 500 - 700 g / m 2 .

[0012] Preferably, the areal density of the negative electrode sheet > 200 g / m 2 , where the areal density can be 210 g / m 2 , 250 g / m 2 , 300 g / m 2 , 310 g / m 2 , 320 g / m 2 , 330 g / m 2 , 340 g / m 2 , 350 g / m 2 , 360 g / m 2 , 370 g / m2 , 380 g / m 2 , 390 g / m 2 , 400 g / m 2 , 450 g / m 2 or 500 g / m 2 etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. Preferably, it is 300 - 400 g / m 2 .

[0013] Preferably, the negative electrode plate is a silicon-based negative electrode plate, and the silicon content of the silicon-based negative electrode plate is 5 - 50%. The silicon content can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% etc., but not limited to the listed values. Other unlisted values outside this numerical range are equally applicable. Preferably, it is 15 - 30%.

[0014] Preferably, the substrate includes any one of metal aluminum foil, metal copper foil or composite copper foil.

[0015] Preferably, the thickness of the metal aluminum foil < 16 μm. The thickness can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or 15.5 μm etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. Preferably, it is 8 - 12 μm.

[0016] Preferably, the thickness of the metal copper foil < 8 μm. The thickness can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or 7.5 μm etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. Preferably, it is 3 - 6 μm.

[0017] Preferably, the thickness of the composite copper foil < 6 μm. The thickness can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or 5.5 μm etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0018] As a preferred technical solution of the present invention, the first coating accounts for 10 - 60% of the total surface density of the coating. The surface density can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% etc., but not limited to the listed values. Other unlisted values within this numerical range are equally applicable. Preferably, it is 40 - 50%.

[0019] Preferably, the slurry of the first coating comprises a first coating active material, a first conductive agent, a first binder, and a first solvent.

[0020] Preferably, the first coating active material comprises any one or a combination of at least two of lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), or lithium cobalt oxide (LCO). Typical but non-limiting examples of such combinations include: a combination of NCM and LFP, a combination of LFP and LCO, or a combination of NCM and LCO, etc.

[0021] Preferably, the first coating active material comprises graphite.

[0022] Preferably, by mass fraction, the mass fraction of the first coating active material in the dry material of the first coating is 90-98%, where the mass fraction can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98%, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable, and preferably 95-97%.

[0023] As a preferred technical solution of the present invention, the first conductive agent comprises any one or a combination of at least two of carbon nanotubes, carbon black, or graphite conductive agent. Typical but non-limiting examples of such combinations include: a combination of carbon nanotubes and carbon black, a combination of carbon black and graphite conductive agent, or a combination of carbon nanotubes and graphite conductive agent, etc.

[0024] Preferably, by mass fraction, the mass fraction of the first conductive agent in the dry material of the first coating is 0.1-10%, where the mass fraction can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable, and preferably 0.5-5%.

[0025] As a preferred technical solution of the present invention, the first binder comprises any one or a combination of at least two of polyvinylidene fluoride, polyimide, sodium carboxymethyl cellulose, or styrene-butadiene rubber. Typical but non-limiting examples of such combinations include: a combination of polyvinylidene fluoride and polyimide, a combination of polyimide and sodium carboxymethyl cellulose, a combination of sodium carboxymethyl cellulose and styrene-butadiene rubber, or a combination of polyvinylidene fluoride and styrene-butadiene rubber, etc.

[0026] Preferably, by mass fraction, the mass fraction of the first binder in the dry material of the first coating is 0.1-5%, where the mass fraction can be 0.1%, 0.5%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable, preferably 1-2%.

[0027] As a preferred technical solution of the present invention, the first solvent includes a conventional solvent and the low-boiling solvent.

[0028] Preferably, the low-boiling solvent includes any one or a combination of at least two of trichloroethane, tetrahydrofuran, methanol, ethanol, dichloroethane or acetone, and typical but non-limiting examples of the combination are: a combination of trichloroethane and tetrahydrofuran, a combination of tetrahydrofuran and methanol, a combination of methanol and ethanol, a combination of ethanol and dichloroethane, or a combination of dichloroethane and acetone, etc.

[0029] Preferably, the boiling point of the low-boiling solvent is 25-100 °C, where the boiling point can be 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C or 70 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable, preferably 30-70 °C.

[0030] Preferably, the conventional solvent includes N-methylpyrrolidone.

[0031] Preferably, by volume fraction, the volume fraction of the low-boiling solvent in the slurry of the first coating is 1-10%, where the fraction can be 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable, preferably 2-5%.

[0032] As a preferred technical solution of the present invention, the slurry of the second coating includes a second coating active material, a second conductive agent, a second binder and a second solvent.

[0033] Preferably, the second coating active material is the same as the first coating active material.

[0034] Preferably, by mass fraction, the mass fraction of the second coating active material in the dry material of the second coating is 90-98%, where the mass fraction can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable, preferably 95-97%.

[0035] Preferably, the second conductive agent is the same as the first conductive agent.

[0036] Preferably, by mass fraction, the mass fraction of the second conductive agent in the dry material of the second coating is 0.1-10%, where the mass fraction can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably 0.5-5%.

[0037] Preferably, the second binder is the same as the first binder.

[0038] Preferably, by mass fraction, the mass fraction of the second binder in the dry material of the second coating is 0.1-5%, where the mass fraction can be 0.1%, 0.5%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably 1-2%.

[0039] Preferably, the second solvent includes any one or a combination of at least two of tetrahydrofuran, ethanol or dichloroethane. Typical but non-limiting examples of the combination are: a combination of tetrahydrofuran and ethanol, a combination of ethanol and dichloroethane, or a combination of tetrahydrofuran and dichloroethane, etc.

[0040] The second object of the present invention is to provide a method for preparing an electrode tab as described in the first object, and the preparation method includes:

[0041] Coating the first coating and the second coating on the substrate simultaneously to obtain a coated tab, and drying the coated tab to obtain the electrode tab.

[0042] In the present invention, the coating needs to be dried to prepare the electrode tab, and the low-boiling solvent in the product has been removed during drying.

[0043] As a preferred technical solution of the present invention, the simultaneous coating uses a multi-channel die coating.

[0044] Preferably, the drying temperature is 50-150°C, where the temperature can be 50°C, 60°C, 70°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 130°C, 140°C or 150°C, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably 80-120°C.

[0045] Preferably, the drying time is 0.5 to 5 min, where the time can be 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min or 5 min, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably it is 1 to 3 min.

[0046] The third object of the present invention is to provide an application of the electrode tab as described in the first object, and the electrode tab is applied to the field of lithium-ion batteries.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The electrode tab prepared in the present invention does not crack, is suitable for manufacturing tabs of high surface density and other easily cracked systems, and the performance of the tab is better. Description of the Drawings

[0049] Figure 1 It is a structural diagram of the electrode tab in Embodiments 1-5 of the present invention.

[0050] In the figure: 1 - substrate; 2 - first coating; 3 - second coating. Detailed Embodiments

[0051] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0052] Embodiment 1

[0053] This embodiment provides a preparation method of an electrode tab, and the structure of the electrode tab is as Figure 1 shown:

[0054] The electrode tab in this embodiment is a positive electrode tab: An electrode tab includes a 12-μm-thick metal aluminum foil as the substrate 1, and a first coating 2 and a second coating 3 are sequentially coated on the surface of the metal aluminum foil. The second coating 3 prepares a slurry according to the formula of lithium nickel cobalt manganese oxide: carbon black: polyvinylidene fluoride = 96.8: 2.0: 1.2 (the second solvent is a volatile substance and is not included in the powder formulation). The first coating 2 adds ethanol accounting for 5% of the volume fraction of the first coating slurry on the basis of the slurry of the second coating 3. The total coating density of the electrode tab is 550 g / m 2 , and the fraction of the surface density of the first coating 2 in the total coating density of the electrode tab is 50%, and the coating rate is 10 m / min.

[0055] In this embodiment, the drying temperature of the first coating 2 and the second coating 3 is 100 °C, and the time is 2.5 min.

[0056] Example 2

[0057] This example provides a method for preparing an electrode plate. The structure of the electrode plate is as Figure 1 shown:

[0058] The electrode plate in this example is a negative electrode plate: An electrode plate includes a 3-μm-thick metallic copper foil as substrate 1. A first coating 2 and a second coating 3 are sequentially coated on the surface of the metallic copper foil. The second coating 3 prepares a slurry according to the formula of graphite: carbon black: sodium carboxymethyl cellulose: styrene-butadiene rubber = 97.3: 1.0: 0.2: 1.5 (the second solvent is a volatile substance and is not included in the powder formulation). The first coating 2 adds trichloroethane accounting for 2% of the volume fraction of the first coating slurry as the slurry on the basis of the slurry ratio of the second coating 3. The total coating density of the electrode plate is 320 g / m 2 , and the areal density fraction of the first coating 2 in the total coating density of the electrode plate is 40%, and the coating rate is 10 m / min.

[0059] In this example, the drying temperature of the first coating 2 and the second coating 3 is 120 °C, and the time is 1 min.

[0060] Example 3

[0061] This example provides a method for preparing an electrode plate. The structure of the electrode plate is as Figure 1 shown:

[0062] The electrode plate in this example is a positive electrode plate: An electrode plate includes an 8-μm-thick metallic aluminum foil as substrate 1. A first coating 2 and a second coating 3 are sequentially coated on the surface of the metallic aluminum foil. The second coating 2 prepares a slurry according to the formula of lithium nickel cobalt manganese oxide: carbon black: polyvinylidene fluoride = 96.8: 2.0: 1.2 (the second solvent is a volatile substance and is not included in the powder formulation). The first coating 2 adds dichloroethane accounting for 3% of the volume fraction of the first coating slurry as the slurry on the basis of the slurry ratio of the second coating 3. The total coating density of the electrode plate is 550 g / m 2 , and the areal density fraction of the first coating 2 in the total coating density of the electrode plate is 60%, and the coating rate is 10 m / min.

[0063] In this example, the drying temperature of the first coating 2 and the second coating 3 is 80 °C, and the time is 3 min.

[0064] Example 4

[0065] In this example, except that the areal density fraction of the first coating 2 in the total coating density of the electrode plate is replaced by 65%, other conditions are the same as those in Example 1.

[0066] Example 5

[0067] In this embodiment, except that the fraction of the areal density of the first coating 2 in the total coating density of the electrode sheet is replaced by 5%, other conditions are the same as those in Embodiment 1.

[0068] Comparative Example 1

[0069] In this comparative example, except that tetrahydrofuran is not added, other conditions are the same as those in Embodiment 1.

[0070] Comparative Example 2

[0071] In this comparative example, except that ethanol is not added, other conditions are the same as those in Embodiment 2.

[0072] The cracking degree of the electrode sheets in Examples 1-5 and Comparative Examples 1-2 was tested, and the results are shown in Table 1:

[0073] Among them, the test method for the cracking degree of the electrode sheet is:

[0074] Table 1

[0075]

[0076]

[0077] From the above results, it can be seen that: when low-boiling-point substances are added to the first coating, after the electrode sheet enters the oven and is heated, the low-boiling-point substances in the first coating start to volatilize at a lower temperature to generate tiny bubbles, which can destroy the tension generated by capillary action during the drying process of the electrode sheet, thereby inhibiting the cracking of the electrode sheet. It can be seen from Examples 4 and 5 that increasing or decreasing the areal density of the first coating will cause the problem of slight cracking of the electrode sheet. It can be seen from Comparative Example 1 that without adding low-boiling-point substances, the cracking of the negative electrode sheet is serious. It can be seen from Comparative Example 2 that without adding low-boiling-point substances, the cracking of the positive electrode sheet is serious.

[0078] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an electrode sheet, characterized in that, The preparation method includes: Simultaneously coating a first coating and a second coating on a substrate to obtain a coated electrode sheet, and drying the coated electrode sheet to obtain the electrode sheet; The electrode sheet includes a substrate, and the first coating and the second coating are sequentially disposed on the surface of the substrate. The slurry of the first coating includes a conventional solvent and a low-boiling solvent. The conventional solvent includes N-methylpyrrolidone; the volume fraction of the low-boiling solvent in the slurry of the first coating is 1% to 10%; The first coating accounts for 50% to 60% of the total surface density of the coatings.

2. The preparation method according to claim 1, wherein The electrode sheet includes a positive electrode sheet and a negative electrode sheet.

3. The preparation method according to claim 2, characterized in that, The areal density of the positive electrode sheet > 300 g / m 2 .

4. The preparation method according to claim 3, characterized in that, The areal density of the positive electrode sheet is 500 to 700 g / m 2 .

5. The preparation method according to claim 2, wherein The areal density of the negative electrode sheet > 200 g / m 2 .

6. The preparation method according to claim 5, characterized in that, The areal density of the negative electrode sheet is 300 to 400 g / m 2 .

7. The preparation method according to claim 2, characterized in that, The negative electrode sheet is a silicon-based negative electrode sheet, and the silicon content of the silicon-based negative electrode sheet is 5% to 50%.

8. The preparation method according to claim 7, characterized in that, The silicon content of the silicon-based negative electrode sheet is 15% to 30%.

9. The preparation method according to claim 1, characterized in that, The substrate includes any one of aluminum metal foil, copper metal foil or composite copper foil.

10. The preparation method according to claim 9, characterized in that, The thickness of the aluminum metal foil < 16 μm.

11. The preparation method according to claim 10, wherein, The thickness of the aluminum metal foil is 8 to 12 μm.

12. The preparation method according to claim 9, characterized in that, The thickness of the copper metal foil < 8 μm.

13. The preparation method according to claim 12, wherein The thickness of the copper metal foil is 3 to 6 μm.

14. The preparation method according to claim 9, characterized in that, The thickness of the composite copper foil < 6 μm.

15. The preparation method according to claim 1, characterized in that, The slurry of the first coating includes a first coating active material, a first conductive agent, a first binder and a first solvent.

16. The preparation method according to claim 15, wherein, The first coating active material includes any one or a combination of at least two of lithium nickel cobalt manganese oxide, lithium iron phosphate or lithium cobalt oxide.

17. The preparation method according to claim 15, characterized in that, The first coating active material includes graphite.

18. The preparation method according to claim 15, wherein, Calculated by mass fraction, the mass fraction of the first coating active material in the dry material of the first coating is 90% to 98%.

19. The preparation method according to claim 18, characterized in that, Calculated by mass fraction, the mass fraction of the first coating active material in the dry material of the first coating is 95% to 97%.

20. The preparation method according to claim 15, wherein The first conductive agent includes any one or a combination of at least two of carbon nanotubes, carbon black or graphite conductive agent.

21. The preparation method according to claim 15, wherein Calculated by mass fraction, the mass fraction of the first conductive agent in the dry material of the first coating is 0.1% to 10%.

22. The preparation method according to claim 21, wherein, Calculated by mass fraction, the mass fraction of the first conductive agent in the dry material of the first coating is 0.5% to 5%.

23. The preparation method according to claim 15, characterized in that, The first binder includes any one or a combination of at least two of polyvinylidene fluoride, polyimide, sodium carboxymethyl cellulose or styrene-butadiene rubber.

24. The preparation method according to claim 15, wherein, Calculated by mass fraction, the mass fraction of the first binder in the dry material of the first coating is 0.1% to 5%.

25. The preparation method according to claim 24, characterized in that, Calculated by mass fraction, the mass fraction of the first binder in the dry material of the first coating is 1% to 2%.

26. The preparation method according to claim 1, characterized in that, The low-boiling solvent includes any one or a combination of at least two of trichloroethane, tetrahydrofuran, methanol, ethanol, dichloroethane or acetone.

27. The preparation method according to claim 1, characterized in that, The boiling point of the low-boiling solvent is 25 to 100 °C.

28. The preparation method according to claim 27, characterized in that, The boiling point of the low-boiling solvent is 30 to 70 °C.

29. The preparation method according to claim 1, characterized in that, Calculated by volume fraction, the volume fraction of the low-boiling solvent in the slurry of the first coating is 2% to 5%.

30. The preparation method according to claim 1, characterized in that, The slurry of the second coating includes a second coating active material, a second conductive agent, a second binder and a second solvent.

31. The preparation method according to claim 30, characterized in that, The second coating active material is the same as the first coating active material.

32. The preparation method according to claim 30, characterized in that, Calculated by mass fraction, the mass fraction of the second coating active material in the dry material of the second coating is 90% to 98%.

33. The preparation method according to claim 32, characterized in that, By mass fraction, the mass fraction of the second coating active substance in the second coating dry material is 95-97%.

34. The preparation method according to claim 30, characterized in that, The second conductive agent is the same as the first conductive agent.

35. The preparation method according to claim 30, characterized in that, By mass fraction, the mass fraction of the second conductive agent in the second coating dry material is 0.1-10%.

36. The preparation method according to claim 35, characterized in that, By mass fraction, the mass fraction of the second conductive agent in the second coating dry material is 0.5-5%.

37. The preparation method according to claim 30, characterized in that, The second binder is the same as the first binder.

38. The preparation method according to claim 30, wherein, By mass fraction, the mass fraction of the second binder in the second coating dry material is 0.1-5%.

39. The preparation method according to claim 38, characterized in that, By mass fraction, the mass fraction of the second binder in the second coating dry material is 1-2%.

40. The preparation method according to claim 30, wherein, The second solvent includes any one or a combination of at least two of tetrahydrofuran, ethanol or dichloroethane.

41. The preparation method according to claim 1, wherein, The simultaneous coating uses a multi-channel die head for coating.

42. The preparation method according to claim 1, characterized in that, The drying temperature is 50-150 °C.

43. The preparation method according to claim 42, characterized in that, The drying temperature is 80-120 °C.

44. The preparation method according to claim 1, characterized in that, The drying time is 0.5-5 min.

45. The preparation method according to claim 44, characterized in that, The drying time is 1-3 min.

46. Use of an electrode sheet prepared by the preparation method according to any one of claims 1-45, characterized in that, The electrode pole piece is applied to the field of lithium-ion batteries.

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